De-inking waste printed cellulosic stock



United States Patent Ofi ice 3,501,373 Patented Mar. 17, 1970 3,501,373 DE-INKIN G WASTE PRINTED CELLULOSIC STOCK Robert H. Illingworth, Madison, N.J., assignor to Garden State Paper Co. Inc., Garfield, N.J., a corporation of Delaware N Drawing. Continuation-impart of application Ser. No. 193,448, May 9, 1962. This application Nov. 4, 1966, Ser. No. 591,972

Int. Cl. D21c 5/02 US. Cl. 1625 Claims ABSTRACT OF THE DISCLOSURE This invention provides an improved method of deinking waste printed paper. The improved method comprises utilizing as the de-inking agent in aqueous solution a small effective amount of non-ionic surface active agent and a hydrocarbon component, the non-ionic surface active agent corresponding to the formula COPENDING APPLICATION This application is a continuation-in-part of my copending application Ser. No. 193,448, issued as US. Patent 3,446,696, on May 9, 1969.

This invention relates to improvements in de-inking printed waste cellulosic stock.

It is an object of the present invention to provide improved methods and agents for de-inking printed cellulosic material to produce a pulp that can be readily and economically handled on conventional paper making machines to produce newsprint, magazine or book stock.

It is another object of this invention to provide improved processes and agents for de-inking waste printed paper to produce a pulp at least substantially equal, and often superior, in brightness, color and strength to that of virgin pulp.

Still another object of this invention is to provide improved agents and methods capable of de-inking a wide variety of waste printed paper, regardless of the type of ink or method of printing originally employed to produce the printed paper.

Other objects of the present invention will in part be clear and will in part appear hereinafter.

Commercial conversion of waste newspaper, magazine and other types of printed waste cellulosic stock to a pulp capable of re-use in forming paper or other cellulosic products has been a much sought after goal in the paper industry.

Although many processes for de-inking such printed cellulosic material have been heretofore proposed, in general, these have not proved commercially satisfactory. Many of these processes, for example, when tested on a commercial scale with the general run of waste newspaper and junk, fail to yield a pulp suitable for re-use as newsprint, magazine or book stock. The failure may be attributable to the fact that many of these processes drive a significant portion of the ink particles into the cellulosic fibers, thereby rendering the pulp gray and unsatisfactory for use except for the manufacture of low grade paper materials, for example, low grade packaging cartons. Other of these processes are so expensive, time-consuming, laborious and complicated that they are simply not economically feasible.

In co-pending applications there are described processes for de-inking waste newspaper, magazine and other types or printed waste cellulosic stock which utilize, as the active de-inking agent, certain non-ionic detergents, e.g., ethylene oxide adducts of alkyl phenols.

Such non-ionic detergents, by themselves, give satisfactory de-inking results when used with the general runof-the-mill waste newspaper and magazine stock produced; for example, standard planographic, e.g., off-set, printing techniques and inks. With certain waste printed cellulosic stock, however; e.g., paper printed by intaglio such as rotogravure techniques and inks, non-ionic detergents of the type specified above and in the co-pending applications do not, by themselves, accomplish a completely satisfactory de-inking job.

As will be readily apparent, in commercial de-inking, it would be highly advantageous if the process would be able to handle a wide variety of waste printed stock, regardless of the type of ink or printing technique originally used in producing the waste printed paper. Otherwise, a costly and time-consuming paper separation step would have to precede de-inking. The economics of paper deinking are such that a paper separation or classification step could well spell the difference between success and failure.

According to the present invention, it has been discovered that improved de-inking results may be realized by utilizing as the active de-inking agent the combination of 1) a non-ionic detergent, and (2) a hydrocarbon component which can be either an aliphatic hydrocarbon or a chlorinated aromatic hydrocarbon.

This combination of ingredients, when used as described herein, has been found to be effective in de-inking all types of waste printed cellulosic stock, regardless of the type of ink or printing technique originally utilized in producing the paper. The combination is particularly advantageous in that it results in increased brightness of the de-inked stocks and permits greater versatility of processing. Thus, the stock to be de-inked can be added to the aqueous de-inking composition either before or after the aforesaid combination of ingredients is added. Alternatively, the paper can be addedto the reactor before addition of water and de-inking ingredients. As a further advantage, freshly printed newspaper, i.e., overissue news, can be treated immediately without the formation or retention of ink spots or smudges.

The aliphatic hydrocarbon can be saturated or unsaturated but preferably will be substantially saturated. It is also preferably a liquid under the operating conditions. Normally this will be at room temperature. Hence it is preferred that the aliphatic hydrocarbon have a melting point or range below about 40 F. and an initial boiling point or range above about F. and more preferably above about F. There can be employed a mixture of aliphatic hydrocarbons such as is present in various petroleum distillates. When such mixtures are used, the melting and boiling points or ranges specified above are those attributable to the entire mixture. Within this category are such products as solvent naphthas, kerosene, gasoline and alkanes meeting the requirements such as the several isomeric heptanes, octanes and nonanes.

The chlorinated aromatic hydrocarbon should preferably be a liquid under the operating conditions, should be monocyclic and should have at least one chlorine atom attached to an aromatic carbon atom. It is preferred that non-aromatic substituents be avoided except that a single alkyl group having up to four carbon atoms can be a substituent on the aromatic nucleus and in addition, a methyl group may also be present. Thus the chlorinated aromatic hydrocarbon can have the structure wherein the R groups are selected from among chlorine, alkyl having 1 to 4 carbon atoms and hydrogen, at least one R group being chlorine, up to a total of six chlorine substituents, not more than one R being alkyl, except that a second R may be methyl. In the preferred embodiment, there are from one to three chlorine substituents, and all other R groups are hydrogen.

Mixtures of several chlorinated aromatic hydrocarbons meeting the foregoing requirements can be employed, such as a mixture of mono-, di-, and trichlorobenzenes.

Representative chlorinated aromtaic hydrocarbons that can be employed either alone or in mixtures with each other, include chlorobenzene; 1,3-dichlorobenzene; 1,3,5- trichlorobenzene; ortho-chlorotoluene, para-chlorotoluene; para-chloroethylbenzene.

The non-ionic detergents suitable for use may be described as water-soluble synthetic non-ionic surface active agents containing a polyoxyalkylene chain of at least two alkenoxy groups, and derived from alkyl phenolic compounds in which the total number of alkyl carbon atoms is between 4 and 24.

The above defined non-ionic surface active agents operative in the instant invention may be more specifically represented by the general formula wherein R represents the residue of a suitable alkyl phenol, R represents hydrogen or lower alkyl, and n has a value from 2 to 100 or more and usually from about 4 to 30. Compounds of this type are well known in the art and are disclosed along with suitable methods for their preparation in US. Patent 2,946,921. In general, they may be obtained by condensing a polyglycol ether containing the required number of alkenoxy groups or an alkylene oxide such as propylene oxide, butylene oxide, or preferably ethylene oxide, with a suitable alkyl phenol. The amount of alkylene oxide condensed with the alkyl phenol, i.e., the length of the polyoxyalkylene chain, will depend primarily upon the particular compound with which it is condensed. As a convenient rule of thumb, approximately 1 mole of alkylene oxide should be employed for each two carbon atoms in the alkyl phenol. However, the optimum amount of alkylene oxide may readily be determined in any particular case by preliminary test and routine experimentation.

An especially suitable non-ionic detergent is an ethylene oxide adduct of dodecylphenol having a formula corresponding to that indicated above, wherein n is between about 8 and 15. Another particularly suitable non-ionic detergent is a condensation product of nonyl-phenol and ethylene oxide having the structural formula wherein n is an inetger between 8 and 15.

The amounts of non-ionic detergent and aliphatic hydrocarbon or aromatic chlorinated hydrocarbon employed should be carefully controlled. Based on the weight of paper, the amount of each of these materials may vary between about 0.1 and 3.0 percent. Especially good results are obtained when about 0.5 to 1 percent by weight of paper of each material is employed, and this amount is preferred.

The relative proportion of the non-ionic detergent to Parts by wt.

Non-ionic detergent 10-1 Hydrocarbon component 1-10 The temperature of the de-inking solution may vary anywhere from room temperature, e.g., 40 to 70 R, up to the cloud point or volatilization temperature of the non-ionic detergent, or the hydrocarbon component, whichever is the lower, although preferably the de-inking solution is employed at room temperature.

Best results are achieved with the de-inking solutions described herein when they are alkaline in pH and it therefore is desirable that an alkali be included therein. Although any suitable alkali or alkaline earth metal hydroxide or salt may be employed, the alkali metal hydroxides and salts, such as sodium hydroxide, potassium hydroxide, soda ash and the like are preferred. Enough of the alkali should be added to maintain the pH of the de-inking solution between about 7.0 and 11, or even higher, and preferably at least about 7.1.

In preparing the de-inking solution, water is charged to the reactor or pulper and the active de-inking agents described hereinabove added. The de-inking agents are preferably added to the water prior to the addition of the wastepaper.

To the resulting solution is added the printed paper, scrap or junk. Alternately, the printed paper, scrap or junk can be added to the reactor or pulper in the dry state followed by addition of water and de-inking agents in either order or as a mixture. The printed cellulosic charge may, if desired, be shredded by appropriate means prior to treatment. This, however, is not necessary, and the waste material may be treated without shredding or without any subdivision in size whatsoever. It is one of the advantages of this invention that costly shredding or pulping techniques prior to de-inking need not be employed. Thus, the waste material to be de-inked is preferably added to the treating solution in its naturally dry condition, i.e., without being subjected to moisture or water other than that which is normally present in the atmosphere or the waste material can, if desired, be wet or be first slurried or pulped in water.

In general, the percent of cellulosic material by weight of the aqueous treating solution should be below 10 percent and preferably below 6.0 percent, or between about 4.0 and 6.0 percent. Good result are obtained when the de-inking solution contains about 5 to 5.5 percent 'by Weight of paper and this value appears to be optimum. The scrap is retained in the treating solution until substantial defiberization takes place. Depending upon the degree of agitation in the reactor, the time in the reactor may vary between about 10 and 50 minutes, and is usually between about 20 and 40 minutes.

Following treatment, the defibered material is dropped to a chest or other suitable reservoir, after which it is diluted with water to a solid content of between about 0.5 and 1.5 percent, preferably about 1.0 percent, based upon the solution weight.

Following dilution, the pulp is separated from the solution and washed and thickened by well known methods. The resulting pulp is then acidified to a pH of between about 4 and 6.5, preferably between about 4.5 and 5.5, thickened and then formed into a web.

This acidification step has been found to significantly increase the brightnes of the paper produced from the recovered pulp, and also avoids the necessity of bleaching the pulp. Moreover, it has been discovered that acidification tends to set any residual ink particles which may be present, thereby preventing such particles from coming off on the felts and rolls during the web forming step. Such in the practice of the invention, such as from about 0.1% to 1% by weight of the reaction mixture of a sodium silicate such as sodium metasilicate and from about 0.1% to 1% by weight of zinc hydrosulfite or other conventional bleaching agent compatible wih the basic reactants.

a 5 percent solid consistency, or between about a 3 to 8 percent solid consistency in this manner. Cocurrent or counter-current washing, alone or in combination, may be used. The resulting pulp is then acidified to the pH indicated hereinabove by addition thereto of a dilute solution of a suitable acid, as for example, alum, sulfuric acid, S and so forth. The resulting pulp may be finally thickened and formed into a web. The number of thickening and washing steps preceding the acidification step, it should be understood, is not critical, and the number of such treatments will be governed largely by the type of equipment employed. Also, if desired, the pulp may be bleached, using a suitable bleaching agent, following acidification. Ordinarily, however, bleaching is not required. When only acidification is used, the pulp need not be, and preferably is not, washed following acidification.

Various auxiliary additives can be employed, if desired,

residual ink particles in the past have been found to create The following examples are exemplary of the mode of considerable difiiculty and aggravation during web formcarrying out the invention: ing.

The recovered stock may be blended with fresh virgin EXAMPLE 1 sulfate or sulfite stock, or with additional recovered stock 10 2,000 f w te d th i -i ki h i l i to make cellulosic articles, such as newspaper, and so amounts listed below are added to a standard laboratory forth. repulping unit having an impeller which rotates at about A suitable arrangement for carrying out the de-inking 900 rpm. Thereafter 100 grams of dry newspaper is addprocess is illustrated in the accompanying drawing, which ed to the unit and mixing begun. is a flow sheet of the steps in a particularly suitable process The pulping o eration is continued fo ho t room in which the waste paper is added to the treating solution. temperature. The pulp is then washed on a 60 mesh wire As indicated in the drawing, water from an appropriate with a water spray until all of the ink has been removed. source is charged to a suitable reactor or pulper. The rc- The pulp is next immersed in an aquebus solution of sulactor or pulper used in the process is equipped with} fur dioxide which has a pH of about 5 and permitted to stirrer or agitator of any appropriate shape which W111 stand in the solution for 10-15 minutes. The pulp is then agitate and defiber the cellulosic material. If desired, formed into a sheet on a standard laboratory sheet mold bafile plates may be attached to the interior of the redrier. actor to assist the agitation action. In each example below, based on the weight of news- After the water has been charged to the reactor, the, paper, 1.2 percent of an ethylene oxide adduct of dodeccombined de-inking agents described herein are added and ylphenol and an amount of a hydrocarbon component agitation continued until the agents are dispersed and/or as listed below in Table I are employed as the de-inking dissolved. chemicals.

Wastepaper, junk, or other printed cellulosic material Sodium hydroxide is added in an amount of about is then added to the reactor. 0.28% by weight based on the weight of the newspaper It will be understood that the sequence of addition can to raise the pH of the aqueous slurry to about pH 7.5. be easily reversed with the paper being added to the dry Also added as optional ingredients are 0.41% by weight reactor, of sodium silicate and of zinc hydrosulfite, based After a suitable period of time in the reactor, the mixupon the weight of the newspaper.

' ture is dropped to a storage chest which is preferably r The pulp thus produced, when sufiiciently white in apequipped with a suitable agitator. If desired, water may be pearance can readily be handled on conventional paper charged to the chest to reduce the solid content of the mixmaking machines to produce a paper web sheet useful ture therein. The mixture from the chest is then diluted to as newsprint. the solid content indicated hereinabove, and washed and Observations were taken on paper sheets prepared from thickened in a well known manner as, for example, by a 40 the pulp following acidification to determine their average Lancaster three-stage washer and thickener equipped with T.A.P.P.I. standard brightness.

TABLE I Wt. percent of hydrocarbon component Brightness based on Ink Hydrocarbon comweight of remaining Before After Example Newspaper treated ponent newspaper on sheet S02 S02 Control A... Specimen. None Yes 62.7 63.1 1 ..do Mixture of mono-, 0.5 No 63.0 61.8

di- & tri-chloro- Control B"... N.Y. Times Yes 63.9 67.4 2 do 1.0 Small trace 63. 8 66. 2 do.. 1.5 No... 62.7 65.2 Monochlorobenzene. 1. 0 Small trace 66. 6 70. 4 Dichlorobenzene 1.0 Trace 66. 7 70.0 Monochlor0be11zene 1.0 Small trace. 61.5 62.0 Diehlorobenzene 1.0 Small 00.8 62.8 None Yes 62. 3 63. 2

a mesh wire screen. The pulp may be thickened to about EXAMPLE 8 Example 3 is repeated with the exception that an ethylene oxide adduct of nonylphenol is substituted for the ethylene oxide dodecylphenol. Similar results are obtained.

EXAMPLE 9 Example 3 is repeated with the exception that diethylene glycol is substituted for ethylene glycol. Similar results are obtained.

EXAMPLE 10 Example 3 is repeated with the exception that propylene glycol is substituted for ethylene glycol. Similar results are obtained.

Although in the examples the de-inking agents are added to the water directly, it should be understood that the agents may also be introduced into the water in asso- EXAMPLES 11-12 The procedure of Examples 1 to 7 is repeated with the xception that the zinc hydrosulfite was omitted. The pH eveloped and the hydrocarbon components are shown 1 Table II. The specimen treated was the New York nnes.

TABLE II Wt. percent Brightness of hydro Ink re- Hydrocarbon carbon maimng Before After x. component component pH on sheet 80; S

Sovasol #1 1 1. 0 8. 3 None 66. 4 70. 6 l Sovasol #2 2 1. 0 8. 4 None 66.1 71. 0

1 Sovasol #1 is a commercial mixture of aliphatic hydrocarbons derived om petroleum and having the following characteristics:

f t 60 60 F gin/cc. 0.7219 Speci y gravi y o F 115 lnitiall1 btoiling point 1 0%3 f F.. 152 50%-- F 193 90% F. 226

n om

Gaini p Water white 2 Sovasol #2 is a commercial mixture of aliphatic hydrocarbons derived om petroleum and having the following characterlsticsz Specific gravity, 60/60 F gm./cc 0.7139 Initial boiling point F 150 Distillation range:

Color EXAMPLE 13 The procedure of Examples 1 to 7 is repeated using the The brightness obtained ranged from 69 to 70 after reatment with sulfur dioxide.

Although in the examples a batch, or more properly, a emi-batch process is indicated, it should be understood hat the de-inking may be carried out using a continuous rocess, as will be obvious to those skilled in the art.

What is claimed:

-1. In a method of de-inking waste printed paper, the mprovement which comprises utilizing as the de-mkmg tgent in aqueous solution between about 0.1 and 3.0 perent, based on the weight of the printed paper, of each vf a non-ionic surface active agent and a hydrocarbon :omponent, the non-ionic surface active agent correspondng to the formula vherein R represents the residue of an alkyl phenol in vhich the total number of carbon atoms is between 7 and [4, R represents hydrogen or lower alkyl, and n is an nteger of from 2 to 100, and the hydrocarbon compoient being a petroleum distillate aliphatic hydrocarbon raving a boiling point above about 100 F. and a melting )Olnt below about 40 F. or a liquid chlorinated mono- :yclic aromatic hydrocarbon having at least one chlorine ttom attached to an aromatic carbon atom the Weight 13.00 of non-ionic surface active agent to hydrocarbon :omponent being between 10: 1 and 1:10.

2. The method of claim 1 wherein the chlorinated aromatic hydrocarbon is a member selected from the group consisting of monochlorobenzene, dichlorobenzene, trichlorobenzene and mixtures thereof.

3. A composition of matter for de-inking waste printed paper in aqueous solution which comprises a non-ionic surface active agent and a hydrocarbon component, the non-ionic surface active agent corresponding to the formula wherein R represents the residue of an alkyl phenol in which the total number of carbon atoms is between 7 and 24, R represents hydrogen or lower alkyl, and n is an integer of from 2 to 100, and the hydrocarbon component being a petroleum distillate aliphatic hydrocarbon having a boiling point above about F. and a melting point below about 40 F. or a Liquid chlorinated monocyclic aromatic hydrocarbon having at least one chlorine atom attached to an aromatic carbon atom the weight ratio of non-ionic surface active agent to hydrocarbon component being between 10:1 and 1:10.

4. The method of claim 1 wherein the non-ionic surface active agent corresponds to the for-mula wherein R is the residue of alkyl phenol in which the total number of carbon atoms is between 7 and 24.

5. A process for de-inking waste printed paper which comprising pulping printed cellulosic material in an aqueous solution comprising a non-ionic surface active agent and a chlorobenzene component, the non-ionic surface active agent corresponding to the formula wherein R represents the residue of an alkyl phenol in which the total number of carbon atoms is between 7 and 24, R represents hydrogen or lower alkyl, and n is an integer of from 2 to 100, and the chlorobnezene component selected from the group consisting of monochlorobenzene, dichlorobenzenes, trichlorobenzenes and mixtures thereof, the weight ratio of non-ionic surface active agent to chlorobenzene component being between 10:1 and 1:10, the amount of printed cellulosic material being below about 10% by weight of the aqueous solution, and the amount of non-ionic detergent and chlorobenzene each being between about 0.1 and 3 percent, based upon the weight of the cellulosic material, continuing the pulping for between about 10 to 50 minutes, and separating the resulting pulp from the aqueous solution.

6. The method of claim 5 wherein the aqueous solution has an alkaline pH.

7. The method of claim 5 wherein the pH of the pulp is reduced to between about 4.0 and 6.5 following washmg.

8. The method of claim 5 wherein the amount of printed paper charged to the pulper is between about 4.0 and 6.0 percent by weight of the solution.

'9. The method of claim 8 wherein the amount of nonionic detergent and chlorobenzene component is each between about 0.5 and 1.0 percent, based upon the weight of the cellulosic material.

-10. A process for de-inking waste printed paper which comprises pulping printed cellulosic material in an aqueous solution having an alkaline pH comprising a nonionic surface active agent and a petroleum distillate aliphatic hydrocarbon component, the non-ionic surface active agent corresponding to the formula wherein R represents the residue of an alkyl phenol in which the total number of carbon atoms is between 7 and 24, R represents hydrogen or lower alkyl, and n is and integer of from 2 to 100, the aliphatic hydrocarbon component boiling above about 100 F., the quantities by weight of each of the non-ionic surface active agents and the hydrocarbon component being from about 0.1 to

9 3% by weight of the cellulosic material, the amount of printed cellulosic material being below about 10% by weight of the aqueous solution, continuing the pulping for between about 10 to 50 minutes, and separating the resulting pulp from the aqueous solution.

11. A process as in claim 10 wherein the aliphatic hydrocarbon component comprises substantially saturated aliphatic hydrocarbons.

12. A process as in claim 11 wherein the reaction mixture also contains a minor amount of a sodium silicate.

13. A process as in claim 11 wherein the reaction mixture also contains a minor amount of zinc hydrosulfite.

14. A process as in claim 10 wherein the aliphatic hydroca-rbon component is a mixture of aliphatic hydro- 10 F. and having an initial boiling point in excess of about 100 F.

15. A process in claim 14 wherein the mixture of aliphatic hydrocarbons consists essentially of saturated ali- 5 phatie hydrocarbons.

References Cited UNITED STATES PATENTS 3,392,083 7/1968 Illingworth 162-5 HOWARD R. CAINE, Primary Examiner US. Cl. X.R,

carbons, the hydrocarbon mixture being a liquid at 70 15 2, -1 

